The present invention pertains generally to resilient support devices, foam structures, and support devices which include foam structures as an integral component.
In many resilient support structures, such as seating, bedding, and padding applications, foam is used as either the principle shock or load absorbing material, or in combination with a resilient structure such as an array of springs as a topper layer over the ends of the springs. This is commonly done in furniture and mattresses, wherein one or more foam layers overlie a spring array. The foam in this type of application is typically in slab-like form, with planar surfaces which rest upon supporting springs and over which covering or upholstery is laid. In some upholstered applications, such as automobile seating, the foam may be molded or otherwise contoured to a particular shape. For a single support surface, such as the planar sleeping surface of a mattress, a single unibody slab of foam is used to cover the entire surface.
Some attempts have been made to create foam layers which have differing support characteristics. For example, U.S. Pat. No. 5,579,549 describes a pad of fibrous material which is coated with adhesive material in designated areas to alter the firmness of the mattress in those areas. U.S. Pat. No. 5,604,021 describes a multi-layer support pad with regions of differing firmness formed by various layers of convoluted or sculpted foam in combination with underlying slab layers of foam. U.S. Pat. No. 5,701,623 describes a mattress topper having a latex foam core surrounded by border sections of adhesively attached synthetic urethane foam of different density than the latex. U.S. Pat. No. 5,704,085 describes a foam layer in a mattress which has an edge of foam attached by adhesive about a perimeter of a foam layer, wherein the edge foam is of a different type, such as polyurethane which is firmer than the center foam to which it is attached, such as latex. These latter three approaches require the manufacture and assembly of several different pieces of different material, each having a different xe2x80x9cSKUxe2x80x9d number and adding to inventory and production costs.
Relatively recent innovations in foam technology have enabled commercial production of contoured or sculpted foam, and undulating surfaces with peaks and valleys in the foam surface. This can be done with specialized cutting equipment in which blades of various designs create contours in the foam surface, as described for example in U.S. Pat. Nos. 4,683,791; 5,191,824; 5,819,631; 6,142,053 and 6,176,164. Contouring or cutting away portions of the surface of foam changes the support characteristics of the foam in a layered application, even when upholstery or other padding layers are placed over the foam. In the planar or slab-like layers of foam used in mattresses, the layers are dimensioned to cover the entire area of the mattress, or to cover the entire underlying spring array, and any contour or shaping is done across an entire surface area of the layer, giving the layer a modified but uniform support characteristic.
The present invention provides shaped, contoured or sculpted foam for use as a load bearing layer which has variable support characteristics selectively formed about different areas of the layer. Variations in the topical form of the foam are created by patterned voids formed by removal of foam material from an otherwise uniform or planar surface. This type of unibody, multi-dimensional foam layer, when combined with underlying support and topical layers, provides a support system with differing support or feel characteristics corresponding to the areas of differing foam contour.
In accordance with one general aspect of the invention, there is provided a thick comforting upholstery layer for use in a mattress construction where the center section of the layer has foam contoured or extracted in a pattern that results in the foam""s physical properties (important to its cushioning behavior such as ILD and SAG factors) are potentiated, while the outer sides of the layer are left intact. In this manner the foam has supportive firm properties along the sides, while the center or main part of firm provides for a soft or conforming structure. This differential in firmness and support provides for a mattress of exceptional comfort while offering a supporting seating edge. It also results in an effectively larger useful sleeping area by providing increasingly supportive foam along the mattress sides. This unique structure is fabricated from one continuous piece of foam, which is more efficient and cost effective than piecing together dissimilar types of foam to form a single layer. Additionally, the transition from firm to soft can be easily graduated by the applied manufacturing processes so as to be unobtrusive (as compared to the abrupt interface between two different types of foam with different support properties). Additionally, the degree of differentiation in firmness and support can be easily varied over a broad range of desired values by using foams of substantially different properties (density, chemical, composition, ILD/IFD, SAG factor, etc.) and varying the amount/pattern of foam that is extracted by the applied manufacturing processes. In a preferred embodiment, a nominal thickness of a foam layer of the invention is in the range of one inch or greater, and the average density in an approximate range of 1.2 to 5.0 lbs./cu. ft. A preferred IFD approximate range is from about 25 to about 70 lbs./sq. in.